Study of deep space? (10)

I believe the answer is:

oceanology

'study of deep space?' is the definition.
(the study of the ocean, a deep space)

'deep space?' is the wordplay.
'deep' becomes 'ocean' (I've seen this before).
'space?' becomes 'ology' (I am not sure about this - if you are sure you should believe this answer much more).
'ocean'+'ology'='OCEANOLOGY'

I've seen this clue in The Independent.

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